Illuminating device



F'aten ted July 18,1950

' UNITED STATES PATENT OFFICE f ILIIUMINATING nEvIoE '7 Henry W; Trost, Rochester, N. Yi, assignor to Bausch & Lomb Optical Company, Rochester, N. Y., a corporation of New York Application July 18, 1946, Serial No. 684,601

1Claim.

The present invention relates to a surface illuminator and more particularly to a device for illuminating eye testing charts or the like.

It is an object of the present invention to provide a novel device of the above type which is light, compact, and easily constructed by economical manufacturing processes.

It is a further object to provide such a device wherein diffused light rays are reflected indirectly with equal intensity and with overlapping coverage upon a display panel from'opposite sides, the overlapping rays complementing each other to produce a uniform and glareless i1- lumination. 1

It is a further object to provide such a device in the form of a two-section cabinet, one section of which is removable, whereby the inner parts such as the lamp, transformer, mirrors, and other apparatus are exposed and may be easily serviced.

Further objects and advantages will be apparent to those skilled in the art by reference to the following description and accompanying drawing in which:

Fig. 1 is a perspective view of a preferred embodiment of the invention,

Fig. 2 is a sectional view on an enlarged scale taken on the line 22 of Fig. 1, and

Fig. 3 is a fragmentary side elevation of the cabinet in disassembled position, showing the locking mechanism for joining the sections of the cabinet. 1 In Fig. 1 of the drawing, a cabinet of any de sired form generally indicated at H is shown comprising a rear or base section I2 and a demountable section I3. In the preferred form of the invention here shown, the rear or base section I2 is constructed with a rear wall. I4 extending the full height of the cabinet; the'wall I4 being flanked by the angularly disposed walls I5 and I6 which in turn join the side walls I1 and I8. A partial top wall I9 is attached to the side walls I5, I6, I1, and I8 and rear wall I4, and a floor 2|] is provided in the cabinet having the full depth of the assembled cabinet. The front and. sides of the cabinet floor are surrounded by a low wall 2| which joins the side walls I5, IE to form a bottom compartment 22.

The demountable front section I3 of cabinet II is a self-rigid structure embodying a front wall 23 flanked by the angularly-disposed walls 24 and 25 which in turn join the side walls 26 and 21 forming a shape symmetrical with the rear section I2. An aperture 28 is formed in the wall area. A bottom wall 29 and a top'wall 30 are joined to the contiguous side walls 24, 25, 26, 21 and front wall 23, and are vertically spaced so that the top walls I9 and 30 of the rear and frontsections, respectively, are in substantial alignment when the'bottom wall 29 nearly rests on the upper edge of the base wall 2|. Means forattaching the demountable section I3 to the base section |2 are provided in any suitable manner such as a pin-and-slot connection as best shown in Fig. 3 in which the pins 3| are fixed to the front section of the cabinet and the inclinedslots 32 are formed in the edge of the: rear section. The weight of the front section l3, hanging on the pins 3| when engaged in the inclinedslots 32, assures that the sections I2 and I3 remain assembled regardless of vibration or accidental shock. v

A display panel for eye testing charts or the like is provided in the form of a rigid opaque wall 33 mounted mutually parallel to thefront wall 23 and back wall I4 in a position 'to substantially prevent light from within the cabinet from traveling directly forward through the aperture 28. The panel 33 issecured at the top and :bottom to the walls 30 and 29, respectively of the front section I3, and the width of the panel is less than the width of the cabinet I I sufficiently to form vertical elongated passages 34 and 35 along opposite sides thereof.

Means for slidably receiving and retaining a sheet 36 of cardboard or other suitable material against the display panel 33 is provided in the form of slotted guideways 31 and 33 extending along the vertical edges of the panel '33 to accommodate the sheet. Characters 39 may be placed on the sheets 36 in any desired pattern such as those found suitable for eye testing charts. A slot 40, cut through the top wall 33 in alignment with the front surface of the display wall 33, permits the sheets 36 to be inserted into the guideways 31 and 38 from the top thereof without opening the cabinet. Lips 4| and 42 are provided at the mouth of the slot 40 to assist in inserting the sheets 36.

According to the present invention, means are provided for uniformly and indirectly illuminating a display panel with diffused light rays, said means comprising an elongated diffused source of light such as a fluorescent lamp 43 and a front and a rear pair of reflectors or mirrors. The fluorescent lamp 43 extends substantially the full height of the cabinet I and is spaced equally mm; well It coverin a major part Of the front 5;

from the side walls I! and I8 throughout its l ngth. Means are provided. for supporting the lamp 43 on the vertical center line of the back wall [4 in the form of brackets 44 fixed at the top and bottom, respectively, to the back wall l4. Lamp 43 is energized through a lead 45 by any suitable means such as a transformer 45 fixed to the floor 29 of the compartment 22 and connected to a suitable source of power, not shown, and any preferred switch arrangement may be used to control the lamp. Light shields 41, 48, 49, 5|], fixed to the vertical edges of wall 33 so as to extend substantially crosswise of said edges from top to bottom, are provided to control the direction of the difiuse light rays which are pro- Jected upon the sheet 36. It has been determined by research that the brightness of a luminous tube light source is greatest in a centrally-disposed zone between its ends. In, the present device, means are provided for equalizing the vertical distribution of light on the chart 36 to substantially compensate for the longitudinal variation in the brightness of the lamp 43. Such means are in the form of suitable modifications in the profile shape of the light shields 4"! and 49 which extend vertically substantially parallel to the lamp 43. By providing protruding portions such as 50 of any desired shape, the light rays which are projected toward the mirrors 5| and 52 may be cut off to control the amount of light reflected thereby.

The rear pair of reflectors or mirrors 5| and 52 are held in a fixed position by any suitable means such as brackets 5;3 ,across the angularlydisposed walls I5 and i6 of the base section I2; Mirrors 51 and 52. are coextensive in length with the lamp 43 and are set at such an angle with reference thereto that a maximum amount of the light from the lamp is reflected forwardly through the vertical apertures 34 and 35 onto the mirrors 54 and 55 in the front section I3. The front pair of mirrors 54 and 55 are fixedly mounted by any suitable means suchas brackets 56 across the angularly-disposed walls 24 and 25 and. extend vertically to the same height as the rear mirrors. Mirrors 54 and 55 are spaced in the cabinet section I3 so as to receive the light rays passing forwardly through the apertures 34 and 35. In order to provide an indirect uniform illumination on the sheet 36-, the front mirrors 54 and 55 are set at such an angle with reference to the front wall 23v that the. diffused light rays from these mirrors cross and overlap so that the near rays 55 which are reflected from one front mirror are augmented bythe far rays 51 which are reflected from the other front mirror. It has been found by. extensive experimentation that the approximate angle at which the mirrors 54 and 55 may be set to accomplish this result is 28 to the front wall 23. By this method, the additive effect of the diffuse light rays from mirrors 54 and 55 incident on every point ofsthe 4 illuminated surface is substantially the same, thus providing a uniform shadowless illumination thereon.

Although but one form of the invention has been shown and described in detail, it will be understood that other forms are possible and that changes may be made in the proportion, shape, and arrangement of the parts without departing from the spirit of the invention as defined in the appended claim.

I claim:

An eye-testing device comprising a cabinet having a base section and a demountable section, said base section having a rear wall and said demountable section having a front wall and an aperture therein, means for attaching the demountablesection to the base section, an elongated fluorescent lamp extending substantially across and attached to the rear wall substantially along the vertical center line thereof, an opaque display wall fixed in said demountable section parallel to said front wall and having substantially-thesame length as said lamp, said display wallextending entirely; across said aperture and spaced rearwardly therefrom; an eye chart mounted on said display wall, and means for uniformly illuminating saideye chart with diffused light rays, said means including, flat mirrors in optical alignment with said lamp and angularly fixed in said cabinet for reflecting the light rays from said lamp onto the front surface of. said chart with equal intensity, the angle of said mirrors being chosen so as to provide overlapping complementary light rays from opposite sides; andlight shields extending along the vertical borders of said display panel for controlling the direction of the light rays which impinge on said chart,,said light shields having means thereon for equalizing the vertical'distri'bution of light rays from said lamp upon said chart to substantially; compensate for longitudinal variations in the brightness'of said lamp.

HENRY W. TROST.

REFERENCES oirE The following references areof record in the file of this patent:

UNITED STATES PATENTS 

